select deptno,ename,'' comm from (select * from tab1 where comm is not null and deptno=30)
union all
select deptno,'' ename,comm from ( select * from emp where comm is not null and deptno=30)
求解 为什么报错
------解决方案--------------------
to_char(comm,'FM99999999.99')这样就可以了